Synthese von funktionalisierten Diazocinen für die Photopharmakologie, Molekularbiologie und für responsive Materialien
The development of artificial photoswitches, which can change their configuration upon activation with light, has paved the way to numerous applications. These applications include drugs that can be activated in the affected tissue and no longer cause side effects elsewhere in the body, peptide cross-linkers, allowing the investigation of complex interactions in biological systems with high spatiotemporal resolution and stress sensing polymers. So far, many of the available artificial photoswitches were suffering from imperfect photophysical properties limiting their use in practical applications. To achieve this objective, improved systems are required, which overcome the systematic limitations of their predecessors. With high quantum yields and superior switching efficiency, diazocines have the potential to meet these requirements. One major advantage is the fact that already the parent system switches upon irradiation with visible light. The diazocine, often referred to as bridged azobenzene, in contrast to azobenzene is thermally stable in its cis configuration and should thus be suitable for photopharmacology and as a mechanophore in mechanoresponsive materials. Furthermore, it should be advantageous as a cross-linker for macromolecules, since its structure reduces hydrophobic interactions. To demonstrate the applicability of diazocines in a broad range of fields, it was essential to develop a synthesis strategy, allowing specific functionalization. The synthesis started from commercially or synthetically available 2 nitrotoluene derivatives. These were dimerized in an oxidative C-C coupling and subsequently converted either in reductive or oxidative azo cyclization reactions. In combination with a suitable protecting group strategy, several functional diazocines were synthesized and tested regarding their applicability in photopharmacology, molecular biology and materials science. In collaboration, diazocine-based synthetic neurotransmitters were synthesized and used to successfully activate and deactivate neuronal signaling and thereby prove the concept of diazocines in photopharmacology. Furthermore, it was shown that diazocines are suitable cross-linkers in both artificial and bio macromolecules.